1. Field of the Invention
The field of the invention is compositions for and methods of killing nematodes.
2. Description of the Prior Art
Agricultural losses due to parasites have always been a major area of concern for most of the nations throughout the world. It is reported that agriculture industry suffers an estimated loss of $157 billion each year due to plant-parasitic nematodes (Abad et al., 2008). Due to such massive monetary losses, plant-parasitic nematodes are attracting the attention of scientists with Meloidogyne incognita being the major parasite of concern. M. incognita is a root knot nematode that has the ability to cause infection in more than 2,000 species of plants.
Although chemical nematicides have been successfully used to control plant-parasitic nematodes, these chemicals are toxic (Li et al., 2007). Many conventional nematicides used to control plant-parasitic nematodes have been shown to contribute to groundwater contamination and depletion of the ozone layer, to be hazardous to the health of humans and animals, and to be possibly harmful to other beneficial microorganisms present in the rhizosphere. A well-known nematicide, methyl-bromide, has been the most effective compound for the control of plant-parasitic nematodes in the past but has been banned from use because of its damaging effects on ozone layer, human health and environment (Li et al., 2007).
Novel methods of nematode control include building nematode resistance in plants by introducing genes that, when expressed, affect the development of the nematode. One such system induces the expression of proteinase inhibitors; in particular, the cysteine proteinase oryzacystatin-I gene from rice has been used to confer resistance against the potato cyst nematode Globodera pallida (Urwin et al. 1995). Similar expression of a taro cystatin gene in transgenic tomato restricted egg mass formation by more than 30% when compared to untransformed plants (Chan et al. 2010).
Transgenic tomato plants expressing the Bt-endotoxin Crylab inoculated with Meloidogyne spp. demonstrated a significant reduction of nematode egg masses per gram of root tissues (Burrows and De Waele 1997). A very promising strategy is the use of RNA interference (RNAi) technology to silence genes that could support nematode development (Bakhetia et al. 2005; Gheysen and Vanholme 2007). Transgenic methods of killing nematodes are very time consuming and expensive. It takes a lot of time and effort to introduce genes into plants and then ensure those genes are expressed properly. Killing nematodes is much faster and more efficient if a person can place a nematicide composition directly in contact with the nematodes without involving plant gene expression.